1. Field of the Invention
The present invention relates to an automatic TIG welding torch with an integrated consumable-wire feed dedicated to robotic welding.
2. Related Art
A TIG (Tungsten Inert Gas) welding torch fed with welding wire conventionally is in the form of a one-piece body provided with internal arrangements suitable for implementing the welding process to which this torch is dedicated.
Torches may be straight or bent, that is to say the beam leaves along the axis of the torch in the case of a straight torch or perpendicular to the axis of the torch in the case of a bent torch.
In the rear part of the torch, usually called the torch support or mounting, there are flexible or semi-rigid fluid feed lines that are connected to the torch body by a connection system specific to each type of line.
The power supply cables are grouped together by mechanical means, usually by screwing them to the corresponding circuits of the torch, except in the case of liquid- or gas-cooled cables, which are therefore attached appropriately.
A flexible tubular sheath, attached to the rear of the torch by a clip or the like, groups together the cable bundle so as to protect it.
The front part of the torch, again called the torch body, comprises a nozzle for delivering the shielding gas, which nozzle is attached to the torch body by screwing or by any other gripping or similar system, and also an electrode.
The nozzle may be made of metal and may or may not be cooled by a cooling fluid, such as water or a gas; in this case, the nozzle must be electrically insulated from the torch body.
However, the nozzle may also be made of a suitable uncooled insulating material, for example a ceramic.
Moreover, the electrode, usually made of pure tungsten or thoriated tungsten, is held centred in the torch body by a gripping system or the like, in such a way that the nozzle forms a sleeve around the electrode.
Furthermore, a consumable wire feed system is generally provided independently of the torch, that is to say it is firmly attached to the torch body or to the torch support, the torch support being the member that connects the torch to the device for moving it.
Conventionally, as shown in FIG. 1, the filler wire is fed into the weld pool by the feed system 3 tangentially or almost tangentially to the liquid metal, at the rear of the electrode 2 surrounded by the nozzle 1, in the welding direction. Under these normal conditions, the angle B defined by the electrode 2 and the filler wire 3 is about 85° to 90°.
However, it turns out in practice that this type of torch is not suitable for robotic TIG welding as it has several drawbacks.
Thus, although the tangential wire feed is perfectly suitable for an automatic TIG welding process in rigs with parallel jaws, the same is not true in robotic welding in which the aspect of space requirement is of paramount importance in order to weld in any position.
However, it will be readily understood that having a consumable-wire feed system that is provided independently of the torch increases the overall size of the assembly, which goes counter to practical use in robotic welding.
In addition, control of the position of the filler wire relative to the welding direction requires the use of an additional axis of the robot, which complicates the unit, increases its cost and is a source of breakdowns.
Moreover, in TIG welding, it is necessary to use a perfectly sharpened, that is to say pointed, electrode in order to obtain a consistent and reproducible result.
To do this, the electrode must be regularly resharpened in order to compensate for its wear, or even completely replaced if its wear has become too great.
This operation requires the operator to stop the machine, remove the electrode, sharpen or replace it, then refit it and, finally, precisely adjust the respective positions of the electrode and the wire so as to relocate the precise position of the wire at the rear of the electrode and tangentially to the welded joint.
It will be understood that this procedure requires the production machine to be stopped one or more times, to the detriment of the expected performance of a robot used in two or three shifts, this procedure being lengthier the more accurate the positioning of the electrode and the wire has to be.
In view of this, the problem presented is to provide an improved wire-guide/nozzle assembly for an electric arc welding torch and an improved automatic TIG welding torch with consumable-wire feed that do not have the abovementioned drawbacks.
In other words, it is an object of the invention to propose a novel torch architecture for TIG welding with filler wire that allows the wire to be easily and precisely positioned relative to the electrode.